Antistick surface coating



' Patented June 30, 1942 UNITED STATES PATENT OFFICE Clarence WalterWilson, Norco,

to California Fruit Growers Exchang Calif., assignor e, Los,

Angeles, Calif, a corporation of California No Drawing.

Application August 17, 1940, Serial No. 353,125

14 Claims. (Cl. ans-s4) V This invention relates to the coatingofsurfaces to reduce the tendency of those surfaces to stick to othersurfaces. Uses for the invention arise particularly with such materialsas asphalt, bitumen, and more solid pitches. It is also applicable inthe handling of a molasses product known in the trade as hard molasses,and which is in reality a highly concentrated molasses which has somephysical characteristics much like a fairly high melting asphalt. Tackyrubber l es e surfaces also present the problem of stickiness.

Such materials as "asphalt, bitumen, highly concentrated molasses, andtacky rubber present .the problem of sticky surfaces in the handling andshipment of the substances themselves.

I have found that it is possible to produce a non-sticky surface whichcan be used in conjunction with the above mentioned adhesive substancesand which will permit other substances or other articles to be readilyenough removed from the surfaces of said substances to producecommercial satisfaction in the handling of the substances. I do this bythe utilization of the aqueous dispersions of materials commonlyreferred to as pectates. r

Accordingly, an object of my invention is the production of relativelynon-sticky surfaces for use in conjunction with the otherwise adhesivesurfaces of asphalt, bitumen, more solid pitches,

highhr concentrated molasses, tacky rubber, and 80 analagoussubstances."

In applying the invention to the handling and shipping of the abovesubstances, it may be desirable to employ containers and under presentpractices to coat the containers. For example, bags may be formed fromheavy paper and then filled with the substance which has been renderedfluid as by the application of heat. In such practice it is, of course,necessary to remove the paper container from the solidified contentsbefore the contents can be again heated or otherwise utilized. Of thesubstances specifically mentioned above, rubber, of course, will notordinarily in commercial practice be rendered fluid by the use of heat.

Now the surface of an ordinary heavy paper which is available and usefulfor this purpose actually presents a multitude of projecting fibers,and, if the surface of the paper he not coated, the

35 dispersion of, say,

45 formed into to the use of a paper container, I employ crude vpectated pulp of the type described in my Patent 2,132,065. I make anaqueous dispersion from the crude pectated pulp as follows:

The desired quantity of the crude pectafgd pulp is mixed withapproximately '7 0 of its weight of NBAPiO'l and approximately 5% of itsweight of flazafia. This mixture is stirred into an appropfimuantity ofhot, and preferably boiling water to give the concentration of pectatehe dispersion. I prefer to boil the dispersion with rapid agitation forfive minutes. The dispersion is then ready for use or may preferably besomewhat cooled before application.

It may be applied to the surface of the container or to the surface ofthe material of which the container is to be formed, in any desiredmanner, as by means of spraying, dipping, brushing or rolling.

The amount of material to be applied and the square feet of paper, and Imay suitably employ as much as one and one-half to two pounds per 1000square feet. The upper limit will ordinarily be a matter of economics.

When applying the pectate dispersion to a surface of paper or the likeas by means of rolls, I have found that a dispersion containing'2% ofthe pectate by weight flows on very readily, and gives a uniformlycoated surface, and dries to produce a thin coating. On the other hand,a

6% by weight of pectate produces a coating of a thickness desired undersome circumstances. With such a dispersion, I may preferably employ ormore of common soap based on the final batch, or other surface tension40 depressant in' suitable proportions. The soap or other surfacetension depressant is added after the pectate has been dispersed. Theseare not essential when coating paper.

After drying, the coated material may be the interior, to receive themolten asphalt, or 'the like. It will be found that such containers canbe removed or stripped from the solidified contents satisfactorily.

fibers become thoroughly entrapped in the molten Obviously the term P 1the P p s s 1 my invention is equivalent to any substance prematerial,and when the material is solidified, it is found to be practicallyimpossible to remove the paper relatively completely, as must be donefor satisfactory commercial practice.

e. V applying my invention in preferred form 56 Numerous attempts andsuggestions have been senting a similar surface which it is desired tohave readily removable from the asphalt or the containers with thecoated side on- I known. These vary somewhat in their properties.

However, so far as I am at present aware, they all present some degreeof utility in connection with the present invention. Two distinctlydifferent types of ectates are: the type made by 15 gthe processd'closed in Huber Patent No.

' gentle stirring a fine stream of r nir ieral acid, such as Slllfllljg.The coagulum is strained off and 30 washed until the wash water shows notrace of the acid, after which it is dried at not over 70 C. and groundto produce the finished product.

The crude pectated pulp described in my Patent 2,132,065 is producedsubstantially as fol- 5 lows:

Citrus pulp is finely ground and thoroughly washed'withwater. It is thensuspended in suffi cient water to give a fluid mass. Soda ash is addedwith stirring to make the liquid just alkaline to phenolphathalein'(about pH 8.5). The pulp is left in contact with the soda ash for abouttwelve hours, preferably at'about 25 C. Any free liquor is drained offand the pectated pulp is thoroughly washed with water, dewatered, 4.1

ground, and dried.

The dried or undried ctated pulp may be dis-- persed mm by ad fig I00parts of it (dry basis), 12 parts of trisodium phosphg,te and 1.2 partsof sodium hydroxide to 20mm of boil- 5O ing water. e suspension is wellagitated and Eept 'ust alkaline to phenolphthalein for, say, fifteenminutes. It is then ready for use as such, or may be diluted.

Purified fibrous" pectates may be prepared 55 from the above dispersionby filtration to remove pulp particles, and precipitating with anapproximately equal volume of alcohol.

The alkali pectates obtained by the above process are fibrous inappearance, in contrast to the co non-fibrous character of pectates madeby other processes, and I refer to them as fibrous pectates. P

It will be obvious to those skilled in the art that other specificphosphates and other specific 05 alkali'es may be used in place of theparticular ones mentioned hereinabove for dispersion purposes.

For the purpose of the present invention I prefer for commercial andeconomic reasons to 70 utilize the fibrous type of pectate, made asdisclosed in my Patent No. 2,132,065, and in particular the crudefibrouspectated pulp therein described. This material possesses ease andcheapness of manufacture, and reliability of ac- 7 tion in connectionwith the present invention, which I regard as outstanding advantages.

As indicated above, this invention. is useful under circumstances whereit may be desired to prevent asphalt, bitumen, tacky rubber, and thelike surfaces from sticking or to reduce the tendency to do so; and theaqueous dispersion may be applied to the desired surfaces in a varietyof ways, as by spraying it upon articles already coated with asphalt, orby dipping them in the aqueous dispersion.

When bodies composed of tacky rubber or having tacky rubber surfaces oresubjected to serious deformation, the surface c ating herein de--scribed may undergo suflicient cracking to permit the bodies to sticktogether to a considerable extent.

Asphalt and bitumen are very commonly em ployed for the purpose ofcoating a variety. of objects where a heavy and resistant protectivecoating is required. An example is the coating of pipes which may beexposed to many different conditions. In applying the invention to thecoating of such objects I may either spray the pectate dispersion on thecoated object or dip the object after coating into the pectatedispersion, depending upon the size, weight, and shape of the articleand convenience in handling. When the dispersion is to be applieddirectly to the surface of the asphalt, bitumen, or the like, I find itpreferable to employ soap or other suitable surface tension' depressantin the manner and amount hereinabove described in order to obtainsatisfactory spreading of the fluid film over the asphalt or othersubstance.

Having thus described my invention in such surfaces of asphalt, bitumen,and the like,'

which comprises placing in immediate juxtaposition with the surface acoating containing effective quantities of pectate.

2. A method of rendering articles coated with asphalt, bitumen, and thelike, non-sticky .at the surface, comprising applying to the surface acoating containing efiective quantities of pectate.

3. In the manufacture of transportation packages of asphalt,bitumen,.and the like,'the step comprising coating at least the interiorsurface of the material of the container with a coating containingquantities of pectate sufiicient to permit ready separation of thecontainer from the contents thereof.

4. As a new article of manufacture, a body having a surface composed ofasphalt,, bitumen, tacky rubber, or the like, the surface being coatedwith acoating containing effective quantities of pectate, whereby thesurface is rendered relatively non-sticky.

5. A transportation package comprised of asphalt, bitumen, highlyconcentrated molasses, or the like, within a removable container, and acoating on the interior of the container comprised of pectate, whichperfects the transportation package in rendering the container readilyremovable.

6. As a new article of manufacture a container formed from paper, or thelike, and adapted for use'in the handling of asphalt, bitumen, highlyconcentrated molasses, and like substances, said container having on itsinterior creases 3 surface a coating containing effective quantities ofpectate, which perfects the container for the use designated. a

7. As a new article of manufacture paper adapted for use as a containerfor asphalt, bi-

tumen, highly concentrated molasses, and like substances, and having acoating containing pectate in amounts not less than about pound ofpectate per 1000 square feet of paper, which perfects the paper for usein a container for asphalt. bitumen, highly concentrated molasses, andlike substances, and permits ready separation of a container made. fromsaid paper from the contents thereof.

8. A method of minimizingadherence between sticky substances such asasphalt, bitumen, and

the like. and a material such as paper and the having an outer normallysticky surface consisting of asphalt, bitumen, or the like, whichcomprises applying to the surface of such articlean aqueous dispersionof pectate, the dispersion includins a surface tension reducing agent.

11. A method of rendering non-sticky articles having an outer normallysticky surface consisting of asphalt, bitumen, or the like, whichcomprises applying to the surface of such article an aqueousdispersion'of pectate to form a coating containing not less thanone-half pound of pectate per thousand square feet of article surface.

12. A method of rendering non-sticky articles having an outer normallysticky surface consisting of asphalt, bitumen, or the like, whichcomprises applying to the surface of such article an aqueous dispersionof pectate, thedispersion. including a surface-tension reducing agent,to form a coating containing not less .than one-half pound of pectateper thousand square feet of article surface.

13. A method of producing relativeiy nonsticky surfaces of asphalt,bitumen, and, the like,

which, comprises placing in immediate juxtaposition with the surface acoating containing effective quantities of fibrous pectatee 14. As vanew article of manufacture, abody having a surface composed of asphalt,bitumen,-

tacky rubber, or the like, the surface being coated with a coatingcontaining eflective quantities v of fibrous pectate, whereby thesurface is rendered relatively non-sticky.

CLARENCE WALTER WILSON.

